Holographic storage media

ABSTRACT

Described are holographic storage mediums and method of making holographic storage mediums. The holographic storage mediums may have write components that bind to the matrix to form a pattern in the media. The holographic storage mediums may also be rewriteable.

FIELD OF THE INVENTION

This invention relates to holographic storage media. In particular, thisinvention relates to rewriteable holographic storage media and methodsof making rewriteable holographic storage media. In addition, thisinvention relates to holographic storage media in which binding ofchemical species to the matrix occurs during hologram recording.

BACKGROUND

Holographic storage systems are storage systems that use holographicstorage media to store data. Holographic storage media includesphotorefractive materials that can take advantage of the photorefractiveeffect described by David M. Pepper et al., in “The PhotorefractiveEffect,” Scientific American, October 1990 pages 62-74. The index ofrefraction in photorefractive materials can be changed by light thatpasses through them. Holographic storage media also includephotopolymers, such as those described in Coufal et al., “Photopolymersfor Digital Holographic Storage” in HOLOGRAPHIC DATA STORAGE, 199-207(2000), and photochromic materials. By controllably changing the indexof refraction in such materials, high-density, high-capacity, andhigh-speed storage of information in holographic storage media can beaccomplished.

In the typical holographic storage system, two coherent light beams aredirected onto a storage medium. The first coherent light beam is asignal beam, which is used to encode data. The second coherent lightbeam is a reference light beam. The two coherent light beams intersectwithin the storage medium to produce an interference pattern. Thestorage medium records this interference pattern by changing its indexof refraction to form an image of the interference pattern.

The recorded information, stored as a holographic image, can be read byilluminating the holographic image with a reference beam. When theholographic image is illuminated with a reference beam at an appropriateangle, a signal beam containing the information stored is produced. Mostoften the appropriate angle for illuminating the holographic image willbe the same as the angle of the reference beam used for recording theholographic image. More than one holographic image may be stored in thesame volume by, for example, varying the angle of the reference beamduring recording.

Varying the angle of the reference beam during recording to storemultiple holographic images in the same volume is called anglemultiplexing. In addition to angle multiplexing, other techniques forstoring multiple holograms in the same volume include wavelengthmultiplexing, phase code multiplexing, correlation multiplexing, shiftmultiplexing, aperture multiplexing, and fractal multiplexing. Since thesame volume can be used to store multiple holographic recordings, highstorage capacities can be obtained using holographic storage systems.

Information can be encoded within the signal beam in a variety of ways.One way of encoding information into a signal beam is by using anelectronic mask, called a spatial-light modulator (SLM). Typically, aSLM is a two dimensional matrix of pixels. Each pixel in the matrix canbe directed to transmit or reflect light, corresponding to a binary 1,or to block light, corresponding to a binary 0. The signal beam, onceencoded by the SLM, is relayed onto the storage medium, where itintersects with a reference beam to form an interference pattern. Theinterference pattern records the information encoded in the signal beamto the holographic storage medium.

The information recorded in the holographic storage medium is read byilluminating the storage medium with a reference beam. The resultingsignal beam is then typically imaged onto a sensor, such as a ChargeCoupled Device (CCD) array or a CMOS active pixel sensor. The sensor isattached to a decoder, which is capable of decoding the data.

FIG. 1 illustrates the basic components of a holographic system 100.System 100 contains a SLM 112, a holographic storage medium 114, and asensor 116. SLM 112 encodes beam 120 with an object image. The image isstored by interfering the encoded signal beam 120 with a reference beam122 at a location on or within holographic storage medium 114. Theinterference creates an interference patterns (or hologram) that iscaptured within medium 114 as a pattern of, for example, a holographicrefractive index grating.

It is possible for more than one holographic image to be stored at asingle location, or for a holographic image to be stored at a singlelocation, or for holograms to be stored in overlapping positions, by,for example, varying the angle, the wavelength, or the phase of thereference beam 122, depending on the particular reference beam employed.Signal beam 120 typically passes through lenses 130 before beingintersected with reference beam 122 in the medium 114. It is possiblefor reference beam 122 to pass through lenses 132 before thisintersection. Once data is stored in medium 114, it is possible toretrieve the data by intersecting a reference beam 122 with medium 114at the same location and at the same angle, wavelength, or phase atwhich a reference beam 122 was directed during storage of the data. Thereconstructed data passes through one or more lenses 134 and is detectedby sensor 116. Sensor 116, is for example, a charged coupled device oran active pixel sensor. Sensor 116 typically is attached to a unit thatdecodes the data.

A holographic storage medium includes the material within which ahologram is recorded and from which an image is reconstructed. Aholographic storage medium may take a variety of forms. For example, itmay comprise a film containing dispersed silver halide particles,photosensitive polymer films (“photopolymers”) or a freestandingphotorefractive crystal such as iron-doped LiNbO₃ crystal.

In the typical photosensitive polymer type holographic storage media,the interference pattern is formed within the media by an irreversiblepolymerization reaction. In this typical storage media, the matrix doesnot react during the recording of the hologram to the media. The writecomponents, which are defined as components that react during hologramformation to form the hologram, are separate from the matrix components,which form the matrix. The write components within the matrix, which caninclude one or more photoreactive monomers, react when exposed to aninterference pattern to form a polymer in the exposed regions. Thehologram is recorded within the matrix as an index modulation formedbetween the polymerized write components and the matrix.

The write components can be entirely different chemical compounds thanthe matrix components. For example, the write components could be chosenso that they react under different conditions than the matrixcomponents. In this way, little reaction of the write components duringmatrix formation occurs.

Alternatively, the same chemical component can be used as both a matrixcomponent and as a write component. For example, acrylate monomers canbe used both as a matrix component, for matrix formation, and as writecomponent, for recording holograms, see for example, U.S. Pat. No.5,874,187. Although acrylate monomers are used to form both the matrixand to form holograms, the matrix component monomers that react to formthe matrix do not substantially react during hologram formation.Although some matrix polymer chains may propagate during hologramwriting, the holograph is generally created by new chains that compriseacrylate monomers that are not part of the matrix.

U.S. Pat. No. 6,103,454, entitled RECORDING MEDIUM AND PROCESS FORFORMING MEDIUM, the disclosure of which is hereby incorporated byreference, generally describes several types of photopolymers for use inholographic storage media. The patent describes an example of creationof a hologram in which a photopolymer is exposed to information carryinglight. The matrix components do not substantially react to form apattern during the recording of the hologram to the media. A monomer,which is not part of the matrix, polymerizes in regions exposed to thelight. Due to the lowering of the monomer concentration caused by thepolymerization, monomer from darker unexposed regions of the materialdiffuses to the exposed regions. The polymerization and resultingconcentration gradient creates a refractive index change forming ahologram representing the information carried by the light.

W. K. Smothers et al., “Photopolymers for Holography,” SPIE OE/LaserConference, 1212-03, Los Angeles, Calif., 1990, describes aphotoimageable system containing a liquid monomer material (thephotoactive monomer) and a photoinitiator (which promotes thepolymerization of the monomer upon exposure to light), where thephotoimageable system is in an organic polymer host matrix that issubstantially inert to the exposure light. During writing of informationinto the material (by passing recording light through an arrayrepresenting data), the monomer polymerizes in the exposed regions. Dueto the lowering of the monomer concentration caused by thepolymerization, monomer from the dark, unexposed regions of the materialdiffuses to the exposed regions. The polymerization and resultingconcentration gradient create a refractive index change, forming thehologram representing the data. Again, as in U.S. Pat. No. 6,103,454,the host matrix does not substantially react during hologram formation.

The prior art has been concerned with the formation of holograms in amedium in which the matrix is substantially inert during the formationof a pattern in the medium. A medium in which reaction with the matrixis exploited as the method for pattern formation has, until now, notbeen achieved.

In addition, rewriteable holographic storage media is being developed.For example, U.S. Reissue Pat. No. 37,658 E, entitled CHIRAL OPTICALPOLYMER BASED INFORMATION STORAGE MATERIAL, describes an optical storagemedium in which an optically active polymer is used to storeinformation. The storage medium is optically active at temperaturesabove Tg and is optically inactive at temperatures below Tg. Informationcan be repeatedly written to or erased from the optically active polymerby raising the temperature of the optically active medium above Tg. Thistype of system has the drawbacks of requiring the temperature of thestorage medium to be raised above ambient temperatures to storeinformation. Heating of the media can occur by direct absorption oflight, however, this can require the use of very high powered lasers anda highly absorptive media.

A storage media that can be used with efficient lasers under ambientconditions and takes advantage of reversible chemical reactions has notyet been achieved.

SUMMARY OF THE INVENTION

This invention relates to optical articles that can be used forholographic storage. The optical articles can include write componentsthat bind to the matrix of the optical article to record a hologram. Inanother embodiment, optical articles that are rewriteable are disclosed.

In one embodiment the optical article includes a matrix and writecomponents. The write components can be reacted to reversibly bind tothe matrix to form a pattern within the optical article when the articleis exposed to an interference pattern.

Preferably, the write components include anthracenes or acenaphthylenes.Preferably, the reversible binding of the write components to the matrixis a cycloaddition reaction. Preferably, the binding of the writecomponents to the matrix can be reversed by exposing the optical articleto light of a different wavelength than was used to bind the writecomponents to the matrix.

Preferably, the pattern formed within the optical article is arefractive index modulation pattern. Preferably, the matrix comprises anorganic, inorganic polymer or glass. Preferably, the matrix containsfunctional moieties to which the write components can bind when theoptical article is exposed to an interference pattern.

Preferably, the write components contain reactive groups that reversiblybind to functional moieties of the matrix when the optical article isexposed to an interference pattern and wherein the proportion of thematrix functional moieties to write component reactive groups within themedium is at least 1:10. Preferably, the optical article contains aphotosensitizer that induces the binding of the write components to thematrix. Preferably, the optical article is a holographic storage medium.

Another embodiment is a method of rewriteable pattern formation withinan optical article. The method includes writing an interference patternto the optical article by exposing the optical article to a firstinterference pattern; flood curing the optical article by exposing theoptical article to light; erasing the data by exposing the article to apredefined condition; and rewriting an interference pattern to theoptical article by exposing the optical article to a second interferencepattern.

Preferably, the predefined condition is the application of heat.Preferably, the optical article has a Δn of 3×10⁻³ or higher after beingexposed to the second interference pattern. Preferably, the opticalarticle is a holographic storage medium.

Another embodiment is a method of manufacturing an optical article. Themethod of manufacturing the optical article includes mixing a matrixprecursor and a write component together and reacting the matrixprecursor to form a matrix, wherein the matrix contains functionalmoieties to which the write component can bind when the optical articleis exposed to an interference pattern and wherein the write componentscan react by reversible cycloadditions.

Yet another embodiment is an optical article that includes a matrix andwrite components. The write components bind to the matrix to form apattern when exposed to an interference pattern.

Preferably, the pattern formed within the optical article is arefractive index modulation pattern. Preferably, the matrix comprises anorganic or inorganic polymer or glass. Preferably, the matrix containsfunctional moieties to which the write components can bind when theoptical article is exposed to an interference pattern. Preferably, thefunctional moieties are part of a polymer backbone that forms thematrix. Preferably, the functional moieties are attached to the matrixas pendent groups.

Preferably, the write components contain reactive groups that bind tothe functional moieties of the matrix when the optical article isexposed to an interference pattern and wherein the proportion of matrixfunctional moieties to write component reactive groups within the mediumis at least 1:10.

Preferably, the write components contain reactive groups that bind tothe functional moieties of the matrix or to another write component.Preferably, the optical article contains a photosensitizer that inducesthe binding of the write components to the matrix. Preferably, theoptical article is a holographic storage medium.

Another embodiment is a method of forming a pattern within an opticalarticle. The method includes exposing an optical article to aninterference pattern. The write components within the optical articlebind to a matrix to record the interference pattern.

Yet another embodiment is a method of manufacturing an optical article.The method of manufacturing the optical article includes mixing a matrixprecursor and a write component together and reacting the matrixprecursor to form a matrix, wherein the matrix contains functionalmoieties to which the write component can bind when the optical articleis exposed to an interference pattern.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood by reference to the DetailedDescription of the Invention when taken together with the attacheddrawings, wherein:

FIG. 1 is a diagram of a conventional holographic storage system;

FIG. 2 is a diagram of write components binding to functional moietiesthat are attached to the polymer backbone of a matrix;

FIG. 3 is a diagram of write components binding to functional moietiesthat are part of the polymer backbone of a matrix;

FIG. 4 is a diagram of a multifunctional write component that can bindto functional moieties that are attached to the matrix or to other writecomponents;

FIG. 5 is a diagram of a multifunctional write component that can bindto functional moieties that are part of the matrix or to other writecomponents;

FIG. 6 is a diagram of preferred mono-anthracenes bis-anthracenes thatcan be used for rewriteable optical articles;

FIG. 7 is a diagram of Diffraction Efficiency v Angle for the opticalarticle of Example 1 using the interference of two 407 nm laser beams;and

FIG. 8 is a diagram of Diffraction Efficiency v Angle for the opticalarticle of Example 2. The example shows the Diffraction Efficiency forone complete cycle of writing to the optical article, flood curing theoptical article, erasing the optical article and rewriting to theoptical article.

DETAILED DESCRIPTION OF THE INVENTION

Described are optical articles, e.g., holographic recording mediums andmethods of making holographic storage mediums. Information can be storedwithin the optical articles in the form of holographic images.

In one embodiment, the holographic images are formed using reversiblechemical reactions that allow for the optical article to be erasedand/or rewritten multiple times. The optical articles can include one ormore matrix components and write components. At least the writecomponents react during hologram formation to form the hologram.

The write components may react during hologram formation by apolymerization reaction in which the write components react with otherwrite components to form a polymer. The write components may also reactduring hologram formation by attaching to the matrix. Finally, acombination of polymerization and matrix attachment can be employed.

Preferably, some of the write components can bind to the matrix duringhologram formation. In an optical article in which hologram formation isaccomplished only by polymerization of the write components,considerable diffusion of the write component reaction products mayoccur subsequent to writing, which can lead to deterioration of thehologram.

In another embodiment, the optical articles include a matrix thatcontains functional moieties. The functional moieties allow for theattachment of write component species directly to the matrix duringhologram formation in the matrix.

Preferred optical articles can be formed according to this invention bysteps including mixing one or more matrix components and writecomponents. The mixture may also include other ingredients such as aphotosensitizer, plasticizer, cosolvent, and/or other additives. Thematrix components are then cured to form a matrix containing the writecomponents. Preferably, the matrix components and the write componentsare selected such that the write components bind to the matrixcomponents during writing of a pattern to the optical articles.

The matrix can comprise one or more organic or inorganic polymers orglass. Preferably, the matrix is made by combining the matrix componentsand the write components and then polymerizing the matrix components toform a matrix that encompasses the write components.

Preferably, the matrix is formed in situ from a matrix precursor by acuring step (curing indicating a step of inducing reaction of theprecursor to form the polymeric matrix). It is possible for theprecursor to be one or more monomers, one or more oligomers, or amixture of monomer and oligomer. In addition, it is possible for thereto be greater than one type of precursor functional group, either on asingle precursor molecule or in a group of precursor molecules.(Precursor functional groups are the group or groups on a precursormolecule that are the reaction sites for polymerization during thematrix cure.) To promote mixing with the write components, the precursoris advantageously liquid at some temperature between about −50° C. andabout 80° C. Preferably, the matrix polymerization is capable of beingperformed at room temperature. Also preferably, the polymerization iscapable of being performed in a time period less than 5 minutes.

The glass transition temperature (T_(g)) of the optical article ispreferably low enough to permit sufficient diffusion and chemicalreaction of the write components during writing of data. Generally, theT_(g) is not more than 50° C. above the temperature at which writing ofdata is performed, which, for typical holographic recording, means aT_(g) between about 80° C. and about −130° C. (as measured byconventional methods). A plasticizer may be included to enhancediffusion in a high Tg matrix.

Examples of polymerization reactions contemplated for forming matrixpolymers in the invention include cationic epoxy polymerization,cationic vinyl ether polymerization, cationic alkenyl etherpolymerization, cationic alkyl ether polymerization, cationic keteneacetal polymerization, epoxy-amine step polymerization, epoxy-mercaptanstep polymerization, unsaturated ester-amine step polymerization (viaMichael addition), unsaturated ester-mercaptan step polymerization (viaMichael addition), vinyl-silicon hydride step polymerization(hydrosilylation), isocyanate-hydroxyl step polymerization (urethaneformation), isocyanatae-amine step polymerization (urea formation),Diels-Alder step polymerization, anionic polymerization ofcyanoacrylates and other monomers, free radical polymerization ofradically polymerizable monomers/oligomers, and sol-gel reactions toform inorganic or hybrid inorganic/organic networks. Additionally,photoinitiated polymerizations can be used for matrix formations.

Several such reactions are enabled or accelerated by suitable catalysts.For example, cationic epoxy polymerization takes place rapidly at roomtemperature by use of BF₃-based catalysts, other cationicpolymerizations proceed in the presence of protons, epoxy-mercaptanreactions and Michael additions are accelerated by bases such as amines,hydrosilylation proceeds rapidly in the presence of transition metalcatalysts such as platinum, and urethane and urea formation proceedrapidly when tin catalysts are employed. It is also possible to usephotogenerated catalysts for matrix formation, provided that steps aretaken to prevent polymerization of the writing component or bonding ofthe write component to the matrix during the photogeneration of thematrix.

Preferably, the matrix contains functional moieties to which the writecomponents can bind during the writing of the pattern. These functionalmoieties may be present as part of the polymer backbone that forms thematrix or in pendent groups of the matrix.

In FIG. 2 functional moieties 22 are attached to the polymer backbone 20as pendent groups off of the polymer backbone 20. Prior to the writingof the pattern write component 24 is not bonded to the matrix and isable to diffuse through the matrix. During the write phase, writecomponents 24 become attached to exposed locations in the matrix throughfunctional moieties 22.

In FIG. 3 functional moieties 32 are part of the main chain of thepolymer backbone 30. Prior to the writing of the pattern, writecomponents 24 are not bonded to the matrix and are able to diffusethrough the matrix. During the write phase, write components 24 becomeattached to exposed locations in the matrix through functional moieties32.

The matrix may contain components, for example plasicizers, that do notcontribute to producing functional sites for write component attachment.Some plasticizers may not be part of the matrix and may just be freemolecules dissolved in the matrix. These matrix components can adddesirable characteristics to the matrix including increasing thecontrast of images written to the holographic recording mediums. Otherdesirable characteristics can include, improving the ability of thewrite component to diffuse through the matrix, contributing to therefractive index variation between the matrix and the write component,and decreasing the time for pattern formation in an optical article.

The write components are one or more chemical species that are unboundedto the matrix, and are preferably free to diffuse through the matrix ofthe storage medium until data is written to the storage medium. Duringwriting of data, e.g. a hologram, the write components react by bindingto functional moieties of the matrix. In a holographic storage systemdata is written when the write species react in a fashion that matchesthe interference fringes of intersecting beams. The light absorbingspecies can be part of a write component, a matrix functional moiety,some other photosensitizer or light absorbing chromophore (can be a freemolecule, attached to the matrix, or to a write component, so long as itcan transfer absorbed photon energy to the binding groups), or anycombination of the above.

The individual write components may react to form one or more bonds withfunctional moieties of the matrix or with other write components. Somewrite component species in addition to being able to bond to the matrixmay also be able to bond with other write components during writing of apattern to the medium.

The write components may comprise one or more reactive groups that bondto the matrix or to other write components during formation of a patternin the medium. FIG. 4 shows a multifunctional write component 44.Multifunctional write component 44 is capable of bonding to the matrix40 through pendent functional moieties 42 or to other write components44. The write components 44 may have separate reactive groups forbinding to the matrix and to other write components, or these reactivegroups may be essentially equivalent, as in a dimerization.

FIG. 5 shows a multifunctional write component 44 that binds to thematrix 50 through main chain functional moieties 52 or to other writecomponents 44. Again, the write components 44 may have separate reactivegroups for binding to the matrix and to other write components, or thesereactive groups may be the same.

Preferably, the matrix contains functional moieties to which the writecomponents can bind. Preferably, the proportion of functional moietieswithin the matrix to the number of write component reactive groups iscontrolled. The precise ratio of function moieties to write componentsgroups is dependent upon how much matrix attachment occurs relative tothe amount of polymerization. However, preferably, the proportion ofmatrix functional moieties to write component reactive groups within themedium is at least 0.1. More preferably, the proportion of matrixfunctional moieties to write component reactive groups within the mediumis at least 1. Most preferably, the proportion of matrix functionalmoieties to write component reactive groups within the medium is atleast 5.

Suitable write components include molecules containing C—C double bondsthat undergo any of the various types of reversible photocycloadditionreactions. These can include anthracenes, acenaphthylenes,phenanthrenes, and related polyaromatic hydrocarbons, photodieneformation/Diels Alder reaction, and concerted and nonconcerted ene-enereactions (2+2, 4+4, 4+2, 3+2, etc.). Also, metal and organic salts canbe attached to photochelating groups, such as spiro compounds,chromenes, and the like. Nucleotides, such as DNA and RNA, can also beattached to such compounds via strong hydrogen bonding interactions.Polymer bound metal complexes can be used as attachment sites forphotoinsertion of various ligands. Molecules used as photoinitiators forpolymerization reactions can instead be bound to groups, such as C—Cdouble bonds, incorporated in a matrix. Thiols, selenols, tellenols,disulfides, diselenides, ditellurides, and various photoiniferters canbe bound to matrix incorporated enes as well. It should be understoodthat for most of these addition reactions it is possible to reversewhich group serves as the matrix functional moiety, and which serves asthe free write component. This list should in no way be construed ascomplete. It is also possible for a single write component molecule (ormonomer) to contain more than reactive functional group.

Preferably, the write components react during hologram formation by acycloaddition reaction. There are a variety of cycloaddition reactionsthat yield rings of different size, and that can be reversed using lightof shorter wavelength than the wavelength first used to react thecomponents or using heat. Four-member rings (cyclobutanes) can be formedby (2+2) cycloadditions, and 8-membered rings can be formed by (4+4)cycloadditions.

Anthracenes, which are an example of species that undergo (4+4)cycloaddition reactions, are a more preferred type of write component.Anthracenes typically posses a high refractive index and undergo forwardand reverse reactions with a high quantum efficiency and minimal sidereactions. Further, the forward and reverse photoreactions arered-shifted into visible wavelengths relative to many of the (2+2)cycloadditions.

FIG. 6 illustrates an example of preferred mono-anthracenes and thereversible reactions they will undergo. In addition, several preferredbis-anthracenes that can be used for rewriteable holography areillustrated.

The photoaddition reactions that the write components undergo to formthe holograms may be reversed by several different methods dependingupon the specific write component chosen. Preferred methods of reversingthese reactions include irradiation of the medium with light of adifferent wavelength than the wavelength used to write the hologram tothe medium, heating the medium (for example by using an IR laser), or byelectrochemical means.

The write component species may be comprised entirely of reactive groupsthat bond to the matrix during or to other write components duringwriting of the data to the medium. Alternatively, the write componentspecies may comprise additional moieties that impart various attributesto the write component species. These attributes can, for example,include increasing the refractive index of the write component, shiftingthe absorption wavelength of the write component, and/or increasing thesolubility of the write component in the matrix.

Formation of a hologram, waveguide, or other optical article relies on arefractive index contrast (Δn) between exposed and unexposed regions ofa medium. The high refractive index contrast of the medium is do, atleast partly, to diffusion of the write component to exposed regions.When a medium is exposed during formation of a pattern, the writecomponent in the exposed regions is consumed by bonding to the matrixand/or bonding to other write components in the region. Unreacted writecomponents from unexposed regions of the matrix can diffuse to theexposed regions of matrix as the write component is consumed. If thewrite component has a different refractive index than the matrix,diffusion of the write component from the unexposed regions willincrease the contrast between exposed and unexposed regions of a medium.

High index contrast is desired because it provides improved signalstrength when reading a hologram, and provides efficient confinement ofan optical wave in a waveguide. One way to provide a high index contrastbetween the matrix and the write component is to use a write componenthaving moieties (referred to as index-contrasting moieties) that aresubstantially absent from the matrix, and that exhibit a refractiveindex substantially different from the index exhibited by the bulk ofthe matrix. For example, high contrast would be obtained by using amatrix that contains primarily aliphatic or saturated alicyclic moietiesand light nonpolarizable atoms (e.g. F, O, B; providing low index) and aphotoactive monomer made up primarily of aromatic groups or conjugateddouble bond systems and heavy polarizable atoms (e.g. S, Se, Te, Br, I;providing high index).

In addition to the write component, the optical articles may contain aphotosensitizer (the photosensitizer, the write component, and thematrix functional moieties being part of the overall photoimageablesystem). The photosensitizer, upon exposure to relatively low levels ofrecording light, instigates the binding of the write component to thematrix or to other write components, avoiding the need for directlight-induced bonding of the write component. The photosensitizerfunctions by absorbing light and entering an excited state. The absorbedphoton energy is then transferred from the photosensitizer to either awrite component or a matrix functional moiety to induce reaction of thewrite components to the functional moiety and thereby return thephotosensitizer to its ground state. The photosensitizer is then free toinitiate binding of additional write components by absorbing additionalphotons, hence functioning as a catalyst. A photosensitizer enablestuning of the writing wavelength and control of the absorptivity of themedia at the writing wavelength. Typically, 0.01 to 5 wt. %photosenstizer, based on the overall media weight, provides desirableresults. Applicable photosenstizers can be chosen from a knowledge ofphotochemistry, the chemical literature, and the Handbook ofPhotochemistry (Steven Murov, Marcel Dekker, 1973).

Preferably, the reaction by which the matrix component is polymerized toform the matrix is independent from reactions by which the writecomponents and matrix components react during writing of a pattern,e.g., data. Media which utilizes a matrix component that reacts to formthe matrix and a write component that reacts by non-independentreactions often experience substantial cross-reaction between theprecursor and the write component during the matrix cure (e.g., greaterthan 20% of the write component is reacted or incorporated into thematrix after cure), or other reactions that inhibit polymerization ofthe write component. Cross-reaction tends to undesirably reduce therefractive index contrast between the matrix and the write component. Inaddition, cross reaction reduces the amount of write component that canbind to the matrix during writing of a pattern and reduces the number ofsites on the matrix that can be bonded to during writing of the pattern.

To be independent, preferably the matrix precursor and the writecomponent are selected such that: (a) the reaction to form the matrixand the reaction to bind the write component to the matrix duringformation of a pattern proceed by different types of reactionintermediates, (b) neither the matrix intermediate nor the conditions bywhich the matrix is polymerized will induce substantial reaction of thewrite component.

A holographic recording medium of the invention can be formed byadequately supporting the photorecording material, such that holographicwriting and reading is possible. Typically, fabrication of the mediuminvolves depositing the matrix precursor/write component mixture betweentwo plates. The plates are typically glass, but it is also possible touse other materials transparent to the radiation used to write data,e.g., a plastic such as polycarbonate, poly(methyl methacrylate), oramorphous polyolefin. It is possible to use spacers between the platesto maintain a desired thickness for the recording medium. During thematrix cure, it is possible for shrinkage in the material to createstress in the plates, such stress altering the parallelism and/orspacing of the plates and thereby detrimentally affecting the medium'soptical properties. To reduce such effects, it is useful to place theplates in an apparatus containing mounts, e.g., vacuum chucks, capableof being adjusted in response to changes in parallelism and/or spacing.In such an apparatus, it is possible to monitor the parallelism inreal-time by use of a conventional interferometric method, and make anynecessary adjustments during the cure. Such a method is discussed, forexample, in U.S. patent application Ser. No. 08/867,563, the disclosureof which is hereby incorporated by reference.

The photorecording material of the invention is also capable of beingsupported in other ways. For instance, it is conceivable to dispose thewrite component (and other components) into the pores of a substrate,e.g., a nanoporous glass material such as Vycor (Vycor can befunctionalized with attachment groups for the write component usingagents such as silane coupling agents, or matrix precursors can beinfused and polymerized within the pores.). More conventional polymerprocessing is also invisioned, e.g., closed mold formation or sheetextrusion. A stratified medium is also contemplated, i.e., a mediumcontaining multiple substrates, e.g., glass, with layers ofphotorecording material disposed between the substrates.

The medium of the invention is then capable of being used in aholographic system, such as discussed previously. The amount ofinformation capable of being stored in a holographic medium isproportional to the product of: the refractive index contrast, Δn, ofthe photorecording material, and the thickness, d, of the photorecordingmaterial. (The refractive index contract, Δn, is conventionally known,and is defined as the amplitude of the sinusoidal variations in therefractive index of a material in which a plane-wave, volume hologramhas been written. The refractive index varies as: n(x)=n₀+Δn cos(K_(x)),where n(x) is the spatially varying refractive index, x is the positionvector, K is the grating wavevector, and n₀ is the baseline refractiveindex of the medium. See, e.g., P. Hariharan, Optical Holography:Principles, Techniques, and Applications, Cambridge University Press,Cambridge, 1991, at 44).

The Δn of a material is typically calculated from the diffractionefficiency or efficiencies of a single volume hologram or a multiplexedset of volume holograms recorded in a medium. The Δn is characteristicof a medium before writing, but is observed by measurement performedafter recording. Advantageously, the photorecording material of theinvention is capable of exhibiting a Δn of 3×10⁻³ or higher.

If the media is a rewriteable type media, preferably, the medium is alsocapable of exhibiting a Δn of 3×10⁻³ or higher after being written to,erased and then being rewritten to again. Preferably, the reduction ofΔn in subsequent rewrite cycles is controlled.

Examples of other optical articles include beam filters, beam steerersor deflactors, and optical couplers. (See, e.g., L. Solymar and D.Cooke, Volume Holography and Volume Gratings, Academic Press, 315-327(1981), the disclosure of which is hereby incorporated by reference.) Abeam filter separates part of an incident laser beam that is travelingalong a particular angle from the rest of the beam. Specifically, theBragg selectivity of a thick transmission hologram is able toselectively diffract light along a particular angle of incidence, whilelight along other angles travel undeflected through the hologram. (See,e.g., J. E. Ludman et al., “Very thick holographic nonspatial filteringof laser beams,” Optical Engineering, Vol. 36, No. 6, 1700 (1997), thedisclosure of which is hereby incorporated by reference.) A beam steereris a hologram that deflects light incident at the Bragg angle. Anoptical coupler is typically a combination of beam deflectors that steerlight from a source to a target. These articles, typically referred toas holographic optical elements, are fabricated by imaging a particularoptical interference pattern within a recording medium, as discussedpreviously with respect to data storage. Medium for these holographicoptical elements are capable of being formed by the techniques discussedherein for storage media or waveguides.

Preferably, the optical article is flood cured once one or moreinterference patterns are recorded to the article. An optical article isflood cured by exposing the whole optical article to an intense lightbeam of a wavelength that causes the optically active species within thematrix to react. Flood curing ensures that all write components andreactive matrix components have reacted so that no changes to theinterference patterns occur when reading the recorded interferencepatterns.

As mentioned previously, the material principles discussed herein areapplicable not only to hologram formation, but also to formation ofoptical transmission devices such as waveguides. Polymeric opticalwaveguides are discussed for example in B. L. Booth, “OpticalInterconnection Polymers,” in Polymers for Lightwave and IntegratedOptics, Technology and Applications, L. A. Hornak, ed., Marcel Dekker,Inc. (1992); U.S. Pat. Nos. 5,292,620;and 5,219,710,the disclosures ofwhich are hereby incorporated by reference. Essentially, the recordingmaterial of the invention is irradiated in a desired waveguide patternto provide refractive index contrast between the waveguide pattern andthe surrounding (cladding) material. It is possible for exposure to beperformed, for example, by a focused laser light or by use of a maskwith a non-focused light source. Generally, a single layer is exposed inthis manner to provide the waveguide pattern, and additional layers areadded to complete the cladding, thereby completing the waveguide. Theprocess is discussed for example at pages 235-36 of Booth, supra, andCols. 5 and 6 of U.S. Pat. No. 5,292,620. A benefit of the invention isthat by using conventional molding techniques, it is possible to moldthe matrix/photoimageable system mixture into a variety of shapes priorto matrix cure. For example, the matrix/photoimageable system mixture isable to be molded into ridge waveguides, wherein refractive indexpatterns are then written into the molded structures. It is therebypossible to easily form structures such as Bragg gratings. This featureof the invention increases the breadth of applications in which suchpolymeric waveguides would be useful.

The invention will be further clarified by the following examples, whichare intended to be exemplary.

EXAMPLE 1

The following is an example of a holographic storage medium in which thewrite components bind to the matrix during the recording of a hologram.The holographic medium has a matrix with anthracenyl pendent functionalgroups and free 9-anthracenecarbonitrile as the write component. Theholographic medium was formed from the following components in thestated proportions wt %:

Desmodur N3200 49.0% Ethylene glycol  6.8% N,N-Dimethylformamide (DMF)37.7% 9-Anthracenemethanol (9AM)  3.9% 9-Anthracenecarbonitrile (9ACN) 1.9% Dibutyltin dilaurate  0.7%

The holographic storage medium was formed by mixing all of thecomponents except for the dibutyltin dilaurate together untilhomogeneous. The dibutylin dilaurate was then mixed in with the othercomponents. The medium was then prepared by placing the mixture betweentwo substrates.

The matrix was formed by reacting the polisocyanate and ethylene glycolin the mixture to form a polyurethane matrix. The polyurethane cure wasaccomplished thermally between the two substrates while being catalyzedby the dibutyltin dilaurate.

DMF is a plasticizing agent that is considered a matrix component inregards to its contribution to the refractive index modulation createdduring hologram writing. This plasticizizer enables improved diffusionof the write component and quicker hologram formation. 9AM is a pendentfunctional group on the polyurethane matrix that attaches with theisocynate during matrix curing. 9ACN is the free write molecule thatattaches (binds) to the 9AM pendent group of the matrix during hologramwriting. 9AM groups also bind with each other during writing andcontribute to hologram formation.

FIG. 7 shows a hologram of diffraction efficiency 1% formed in thismedia using the interference of two 407 nm laser beams. As shown in FIG.7, the 9ACN absorbs the light strongly and the 9AM pendent groupsabsorbs it weekly.

EXAMPLE 2

The following is an example of a rewriteable media. The rewriteablemedia uses a matrix attachment approach in which the write componentsare able to bind to the matrix. The holographic medium has a matrix withanthracenyl pendent functional groups and a write components with free9-anthracenecarbonitrile. The holographic medium was formed from thefollowing components in the stated proportions: wt %

Desmodur N3200 49.8% Ethylene glycol  7.2% N,N-Dimethylformamide (DMF)38.1% 9-Anthracenemethanol (9AM)  3.9% 9-Anthracenecarbonitrile (9ACN) 0.3% Dibutyltin dilaurate  0.7%

The holographic storage medium was formed by first mixing all of thecomponents except for the dibutyltin dilaurate together untilhomogeneous. The dibutylin dilaurate catalyst was then mixed in with theother components. The medium was then prepared by placing the mixturebetween two substrates.

The matrix was formed by reacting the polisocyanate and ethylene glycolin the mixture to form a polyurethane matrix. The polyurethane cure wasaccomplished thermally between the two substrates while being catalyzedby the dibutyltin dilaurate.

DMF is a plasicizing agent and cosolvent that is considered a matrixcomponent in regards to its contribution to the refractive indexmodulation created during hologram writing. This plasticizer enablesimproved diffusion of the write component and quicker hologramformation. 9AM is a pendent functional group on the polyurethane matrixthat attaches with the isocyanate during matrix curing. 9ACN is the freewrite molecule that attaches (binds) to the 9AM pendent group of thematrix during hologram writing. 9AM groups also bind with each otherduring writing and contribute to hologram formation.

FIG. 8 shows the diffraction efficiency of one hologramwrite-erase-rewrite cycle using the media of Example 1. In FIG. 8, ahologram is first written to the media hologram of diffractionefficiency 0.0085% formed in this media using the interference of two410 nm laser beams.

In this media, the 9ACN absorbs the light strongly and the 9AM pendentgroups absorbs it weekly, hence ensuring preferential reaction of 9ACNwith matrix 9AM rather than reaction of 9AM groups with each other. Toensure virtually complete reaction of the monomers, the sample is thenflood cured with blue light to bind all remaining unreacted anthracenes(9AM and 9ACN) that can react. Flood curing causes some washing out ofthe hologram, which is evident by the reduced diffraction efficiencyfollowing the flood curing (and a slight angle shift). Attempting towrite to the media using a 410 nm laser at this time results in no newhologram and negligible change in the original hologram. The hologram isthen erased using UV light from a mercury arc lamp passed through aninterference filter having a peak transmission of 290 nm and a bandwidthof 10 nm at half height. After erasing the media has a maximumdiffraction efficiency of 0.0010%. After erasing the original hologram anew hologram is rewritten to the media using a 410 nm laser. Therewritten hologram has a maximum diffraction efficiency of 0.0105%.Accordingly, the maximum diffraction efficiency between the originalhologram and the rewritten hologram is +0.02%. Meaning the rewrittenhologram was actually stronger than the original hologram.

Having now fully described this invention, it will be appreciated bythose skilled in the art that the invention can be performed within awide range of parameters within what is claimed, without departing fromthe spirit and scope of the invention.

1. A holographic storage optical article comprising: a matrix formed insitu using one of cationic epoxy polymerization, cationic vinyl etherpolymerization, cationic alkenyl ether polymerization, cationic alkylether polymerization, cationic ketene acetal polymerization, epoxy-aminestep polymerization, epoxy-mercaptan step polymerization, unsaturatedester-amine step polymerization (via Michael addition), unsaturatedester-mercaptan step polymerization (via Michael addition),vinyl-silicon hydride step polymerization (hydrosilylation),isocyanate-hydroxyl step polymerization (urethane formation),isocyanate-amine step polymerization (urea formation), Diels-Alder steppolymerization, anionic polymerization of cyanoacrylates and sol-gelreactions to form inorganic or hybrid inorganic/organic networks,comprising functional moieties capable of binding to write components;and write components, wherein the write components can be reacted toreversibly bind to functional moieties pendant upon or within the matrixbackbone to form a pattern within the optical article when theholographic storage article is exposed to an interference pattern andwherein the write components are not bonded to the matrix and are ableto diffuse through the matrix prior to reversibly binding to the matrixto form the pattern, and the holographic storage optical article isrewriteable and is configured to store holographic data and haveholographic data retrieved from the article.
 2. The optical article ofclaim 1, wherein the write components comprise an anthracenes.
 3. Theoptical article of claim 1, wherein the reversible binding of the writecomponents to the matrix is a cycloaddition reaction.
 4. The opticalarticle of claim 1, wherein the binding of the write components to thematrix can be reversed by exposing the optical article to light of adifferent wavelength than was used to bind the write components to thematrix.
 5. The optical article of claim 1, wherein the pattern formedwithin the optical article is a refractive index modulation pattern. 6.The optical article of claim 1, wherein the matrix comprises an organicor inorganic polymer or glass.
 7. The optical article of claim 1,wherein the write components contain reactive groups that reversiblybind to functional moieties of the matrix when the optical article isexposed to an interference pattern and wherein the proportion of thematrix functional moieties to write component reactive groups within themedium is at least 1:10.
 8. The optical article of claim 1, wherein theoptical article contains a photosensitizer that induces the binding ofthe write components to the matrix.
 9. The optical article of claim 1,wherein the optical article is a holographic storage medium.
 10. Theoptical article of claim 1, wherein the write components bind to thematrix functional moieties via a dimerization or cycloaddition reaction.11. A method of rewritable pattern formation within an optical article,comprising: writing an interference pattern comprising first data to theoptical article by exposing the optical article to a first interferencepattern, wherein the interference pattern is formed by bonding writecomponents to a matrix comprising functional moieties that are pendantupon or within the matrix backbone and are capable of binding to writecomponents and wherein the write components are not bonded to the matrixand are able to diffuse through the matrix prior to binding to thematrix to form the interference pattern, and wherein the matrix isformed using one of cationic epoxy polymerization, cationic vinyl etherpolymerization, cationic alkenyl ether polymerization, cationic alkylether polymerization, cationic ketene acetal polymerization, epoxy-aminestep polymerization, epoxy-mercaptan step polymerization, unsaturatedester-amine step polymerization (via Michael addition), unsaturatedester-mercaptan step polymerization (via Michael addition),vinyl-silicon hydride step polymerization (hydrosilylation),isocyanate-hydroxyl step polymerization (urethane formation),isocyanate-amine step polymerization (urea formation), Diels-Alder steppolymerization, anionic polymerization of cyanoacrylates and sol-gelreactions to form inorganic or hybrid inorganic/organic networks;erasing the data by exposing the article to a predefined condition;writing a second interference pattern comprising second data to theoptical article by exposing the optical article to a second interferencepattern; and reading the second data from the optical article.
 12. Themethod of claim 11, wherein the optical article comprises anthracenes.13. The method of claim 11, wherein the predefined condition is exposureto light of a different wavelength than was used during the floodcuring.
 14. The method of claim 11, wherein the predefined condition isheat.
 15. The method of claim 11, wherein the optical article has a Δnof 3×10⁻³ or higher after being exposed to the second interferencepattern.
 16. The method of claim 11, wherein the optical article is aholographic storage medium.
 17. The method of claim 11, furthercomprising flood curing the optical article by exposing the opticalarticle to light after writing an interference pattern.
 18. The methodof claim 11, wherein the write components bind to the matrix functionalmoieties via a dimerization or cycloaddition reaction.
 19. A method ofmanufacturing an optical article, comprising: mixing a matrix precursorand a write component together; and reacting the matrix precursor toform a matrix using one of cationic epoxy polymerization, cationic vinylether polymerization, cationic alkenyl ether polymerization, cationicalkyl ether polymerization, cationic ketene acetal polymerization,epoxy-amine step polymerization, epoxy-mercaptan step polymerization,unsaturated ester-amine step polymerization (via Michael addition),unsaturated ester-mercaptan step polymerization (via Michael addition),vinyl-silicon hydride step polymerization (hydrosilylation),isocyanate-hydroxyl step polymerization (urethane formation),isocyanate-amine step polymerization (urea formation), Diels-Alder steppolymerization, anionic polymerization of cyanoacrylates and sol-gelreactions to form inorganic or hybrid norganic/organic networks, whereinthe matrix contains functional moieties that are pendant upon or withinthe matrix backbone to which the write component can bind when theoptical article is exposed to an interference pattern, the writecomponents are not bonded to the matrix and are able to diffuse throughthe matrix prior to exposure to the interference pattern, the writecomponents can react by reversible cycloadditions, and the opticalarticle is rewriteable and is configured to store holographic data andhave holographic data retrieved from the article.
 20. The method ofclaim 19, wherein the write components comprise anthracenes.
 21. Themethod of claim 19, wherein the optical article further comprises aphotosensitizer.
 22. The method of claim 19, wherein the optical articleis a holographic storage medium.
 23. An optical article comprising: amatrix formed in situ using one of cationic epoxy polymerization,cationic vinyl ether polymerization, cationic alkenyl etherpolymerization, cationic alkyl ether polymerization, cationic keteneacetal polymerization, epoxy-amine step polymerization, epoxy-mercaptanstep polymerization, unsaturated ester-amine step polymerization (viaMichael addition), unsaturated ester-mercaptan step polymerization (viaMichael addition), vinyl-silicon hydride step polymerization(hydrosilylation), isocyanate-hydroxyl step polymerization (urethaneformation), isocyanate-amine step polymerization (urea formation),Diels-Alder step polymerization, anionic polymerization ofcyanoacrylates and sol-gel reactions to form inorganic or hybridinorganic/organic networks, comprising functional moieties that arependant upon or within the matrix backbone and are configured to bind towrite components; and write components, wherein the write componentsbind to the matrix to form a pattern when exposed to an interferencepattern and wherein the write components are not bonded to the matrixand are able to diffuse through the matrix prior to binding to thematrix to form the pattern, and the holographic storage optical articleis rewriteable and is configured to store holographic data and haveholographic data retrieved from the article.
 24. The optical article ofclaim 23, wherein the pattern formed within the optical article is arefractive index modulation pattern.
 25. The optical article of claim23, wherein the matrix comprises an organic or inorganic polymer orglass.
 26. The optical article of claim 23, wherein the functionalmoieties are part of a polymer backbone that forms the matrix.
 27. Theoptical article of claim 23, wherein the functional moieties areattached to the matrix as pendent groups.
 28. The optical article ofclaim 23, wherein the write components contain reactive groups that bindto the functional moieties of the matrix when the optical article isexposed to an interference pattern and wherein the proportion of matrixfunctional moieties to write component reactive groups within the mediumis at least 1:10.
 29. The optical article of claim 23, wherein the writecomponents contain reactive groups that bind to the functional moietiesof the matrix or to another write component.
 30. The optical article ofclaim 23, wherein the optical article contains a photosensitizer thatinduces the binding of the write components to the matrix.
 31. Theoptical article of claim 23, wherein the optical article is aholographic storage medium.
 32. The optical article of claim 23, whereinthe T_(g) of the optical article is between 80° C. and −130° C.
 33. Theoptical article of claim 23, wherein the write components bind to thematrix functional moieties via a dimerization or cycloaddition reaction.34. A method of forming a pattern within an optical article, comprising:exposing an optical article to an interference pattern, wherein writecomponents within the optical article bind to a matrix comprisingfunctional moieties that are pendant upon or within the matrix backboneand are capable of binding to write components to record theinterference pattern, the write components are not bonded to the matrixand are able to diffuse through the matrix prior to binding to thematrix to form the pattern, the matrix is formed using one of cationicepoxy polymerization, cationic vinyl ether polymerization, cationicalkenyl ether polymerization, cationic alkyl ether polymerization,cationic ketene acetal polymerization, epoxy-amine step polymerization,epoxy-mercaptan step polymerization, unsaturated ester-amine steppolymerization (via Michael addition), unsaturated ester-mercaptan steppolymerization (via Michael addition), vinyl-silicon hydride steppolymerization (hydrosilylation), isocyanate-hydroxyl steppolymerization (urethane formation), isocyanate-amine steppolymerization (urea formation), Diels-Alder step polymerization,anionic polymerization of cyanoacrylates and sol-gel reactions to forminorganic or hybrid inorganic/organic networks and the holographicstorage optical article is rewriteable and is configured to storeholographic data and have holographic data retrieved from the article.35. The method of claim 34, wherein the pattern formed within theoptical article is a refractive index modulation pattern.
 36. The methodof claim 34, wherein the matrix comprises an organic or inorganicpolymer or glass.
 37. The method of claim 34, wherein the functionalmoieties are part of a polymer backbone that forms the matrix.
 38. Themethod of claim 34, wherein the functional moieties are attached to thematrix as pendent groups.
 39. The method of claim 34, wherein the writecomponents contain reactive groups that bind to the functional moietiesof the matrix when the optical article is exposed to an interferencepattern and wherein the proportion of matrix functional moieties towrite component reactive groups within the medium is at least 1:10. 40.The method of claim 34, wherein the write components contain reactivegroups that bind to the functional moieties of the matrix or to anotherwrite component.
 41. The method of claim 34, wherein the optical articlecontains a photosensitizer that induces the binding of the writecomponents to the matrix.
 42. The method of claim 34, wherein theoptical article is a holographic storage medium.
 43. The method of claim34, wherein the T_(g) of the optical article is not more than 50° C.above the temperature at which the pattern is formed.
 44. The method ofclaim 34, wherein the write components bind to the matrix functionalmoieties via a dimerization or cycloaddition reaction.
 45. A method ofmanufacturing an optical article, comprising: mixing a matrix precursorand a write component together; and reacting the matrix precursor toform a matrix using one of cationic epoxy polymerization, cationic vinylether polymerization, cationic alkenyl ether polymerization, cationicalkyl ether polymerization, cationic ketene acetal polymerization,epoxy-amine step polymerization, epoxy-mercaptan step polymerization,unsaturated ester-amine step polymerization (via Michael addition),unsaturated ester-mercaptan step polymerization (via Michael addition),vinyl-silicon hydride step polymerization (hydrosilylation),isocyanate-hydroxyl step polymerization (urethane formation),isocyanate-amine step polymerization (urea formation), Diels-Alder steppolymerization, anionic polymerization of cyanoacrylates and sol-gelreactions to form inorganic or hybrid inorganic/organic networks,wherein the matrix contains functional moieties that are pendant upon orwithin the matrix backbone and are to which the write component can bindwhen the optical article is exposed to an interference pattern, thewrite components are not bonded to the matrix and are able to diffusethrough the matrix prior to binding to the matrix to form the pattern,and the holographic storage optical article is rewriteable and isconfigured to store holographic data and have holographic data retrievedfrom the article.
 46. The method of claim 45, wherein the matrixcomprises an organic or inorganic polymer or glass.
 47. The method ofclaim 45, wherein the functional moieties are part of a polymer backbonethat forms the matrix.
 48. The method of claim 45, wherein thefunctional moieties are attached to the matrix as pendent groups. 49.The method of claim 45, wherein the write components contain a reactivegroup that binds to the functional moieties of the matrix when theoptical article is exposed to an interference pattern and wherein theproportion of matrix functional moieties to write component reactivegroups within the medium is at least 1:10.
 50. The method of claim 45,wherein the write components contain a reactive group that binds to thefunctional moieties of the matrix or to another write component.
 51. Themethod of claim 45, wherein the optical article contains aphotosensitizer that induces the binding of the write component to thematrix.
 52. The method of claim 45, wherein the optical article is aholographic storage medium.
 53. The method of claim 45, wherein thewrite components bind to the matrix functional moieties via adimerization or cycloaddition reaction.